Ongoing research to measure resistivity through casing has been provided on a co-funded basis from: (a) U.S. Department of Energy Grant No. DE-FG19-88BC14243 entitled xe2x80x9cProof of Feasibility of Thru Casing Resistivity Technologyxe2x80x9d; (b) U.S. Department of Energy (DOE) Grant No. DE-FG22-90BC14617 entitled xe2x80x9cProof of Concept of Moving Thru Casing Resistivity Apparatusxe2x80x9d; (c) U.S. Department of Energy (DOE) Grant No. DE-FG22-93BC14966 entitled xe2x80x9cFabrication and Downhole Testing of Moving Through Casing Resistivity Apparatusxe2x80x9d; and (d) Gas Research Institute (GRI) Contract No. 5088-212-1664 entitled xe2x80x9cProof of Feasibility of the Through Casing Resistivity Technologyxe2x80x9d. The government and the GRI have certain rights in this invention. The application herein was filed during periods of time funded by (c) and (d) above.
This invention provides new apparatus and methods of measurement for inspecting casing within cased wells. The invention provides new apparatus and methods of measurement for locating collars within cased wells. The invention may be used in any cased well, but will find wide application in oil and gas wells in particular that typically possess steel cased boreholes.
The invention provides new apparatus and methods of measurement for inspecting pipelines. The invention may also be used to inspect the walls of oil and gas pipelines. The invention is also useful to locate joints were the oil and gas pipelines are joined.
None of the data herein had been made public before the date of Jul. 8, 1993 wherein one of the inventors herein, William Banning Vail III, gave a verbal presentation entitled xe2x80x9cThrough Casing Resistivityxe2x80x9d to The 1993 Formation Evaluation Technical Advisory Group sponsored by the Gas Research Institute in Chicago, Ill. William Banning Vail III publicly described at that meeting data that was used to unambiguously locate collars for the first time in PML""s Test Well located in Woodinville, Wash.
This invention was conceived as a result of work on another invention, namely inventions conceived to measure the resistivity of geological formations from within cased wells. The oil industry has long sought to measure resistivity through casing. Such resistivity measurements, and measurements of other electrochemical phenomena, are useful for at least the following purposes: locating bypassed oil and gas; reservoir evaluation; monitoring water floods; measuring quantitative saturations; cement evaluation; permeability measurements; and measurements through a drill string attached to a drilling bit. Therefore, measurements of resistivity and other electrochemical phenomena through metallic pipes, and steel pipes in particular, are an important subject in the oil industry. Many U.S. patents have issued in the pertinent Subclass 368 of Class 324 of the United States Patent and Trademark Office which address this subject. The following presents a brief description of the particularly relevant prior art presented in the order of descending relative importance.
U.S. patents which have already issued to the inventor in this field are listed as follows: U.S. Pat. No. 4,820,989 (Ser. No. 06/927,115); U.S. Pat. No. 4,882,542 (Ser. No. 07/089,697); U.S. Pat. No. 5,043,688 (Ser. No. 07/435,273); U.S. Pat. No. 5,043,669 (Ser. No. 07/438,268); U.S. Pat. No. 5,075,626 (Ser. No. 07/434,886); U.S. Pat. No. 5,187,440 (Ser. No. 07/749,136); and U.S. Pat. No. 5,223,794 (Ser. No. 07/754,96); U.S. Pat. No. 5,570,024 (Ser. No. 08/813,615); U.S. Pat. No. 5,633,590 (Ser. No. 08/214,648); U.S. Pat. No. 5,717,334 (Ser. No. 08/508,781); U.S. Pat. No. 6,025,721 (Ser. No. 08/738,924); U.S. Pat. No. 6,031,381 (Ser. No. 08/685,796); U.S. Pat. No. 6,157,195 (Ser. No. 08/864,309). These thirteen U.S. patents are collectively identified as xe2x80x9cthe Vail patentsxe2x80x9d herein.
The apparatus and methods of operation herein disclosed are embodiments of the Through Casing Resistivity Tool(copyright) that is abbreviated TCRT(copyright). The Through Casing Resistivity Tool(copyright) and TCRT(copyright) are Trademarks of ParaMagnetic Logging, Inc. in the United States Patent and Trademark Office. ParaMagnetic Logging, Inc. has its principal place of business located at 18730-142nd Avenue N.E., Woodinville, Wash., 98072, USA, having the following telephone number: (206) 481-5474.
The Through Casing Resistivity Tool(copyright) gives casing inspection information and collar location information as a natural byproduct of its operation. However, that information is useful in its own right and is of commercial value in its own right. Therefore, the invention herein includes any embodiment of the Through Casing Resistivity Tool(copyright) or any portion thereof that is used for the purpose of inspecting casing and/or to determine the location of casing collars. The invention herein includes any embodiment of the Through Casing Resistivity Tool(copyright) or any portion thereof that is used for the purpose of inspecting pipelines and/or to determine the location where such pipelines are jointed together.
An important paper concerning the Through Casing Resistivity Tool(copyright) was published recently. Please refer to the article entitled xe2x80x9cFormation Resistivity Measurements Through Metal Casingxe2x80x9d, having authors of W. B. Vail, S. T. Momii of ParaMagnetic Logging, Inc., R. Woodhouse of Petroleum and Earth Science Consulting, M. Alberty and R. C. A. Peveraro of BP Exploration, and J. D. Klein of ARCO Exploration and Production Technology which appeared as Paper xe2x80x9cFxe2x80x9d, Volume I, in the Transactions of the SPWLA Thirty-Fourth Annual Logging Symposium, Calgary, Alberta, Canada, Jun. 13-16, 1993, sponsored by The Society of Professional Well Log Analysts, Inc. of Houston, Tex. and the Canadian Well Logging Society of Calgary, Alberta, Canada (13 pages of text and 8 additional figures). Experimental results are presented therein which confirm that the apparatus and methods disclosed in Ser. No. 07/434,886 that is U.S. Pat. No. 5,075,626 actually work in practice to measure the resistivity of geological formations adjacent to cased wells. To the author""s knowledge, the SPWLA paper presents the first accurate measurements of resistivity obtained from within cased wells using any previous experimental apparatus. Page 6 of that paper describes attempts to locate casing collars from the data presented. One collar was clearly located, and another one was missed. Therefore, the data presented in that paper did not present compelling evidence that the TCRT(copyright) could routinely locate all the casing collars present nor did it provide a methodology to routinely do so in practice. Page 6 of that paper however shows that different weight casings could be identified with the TCRT(copyright).
A verbal presentation entitled xe2x80x9cIntroduction to the Through Casing Resistivity Toolxe2x80x9d was made to the Permian Basin Well Logging Society on Mar. 18, 1993.
A theoretical paper of considerable importance was published recently concerning resistivity measurements from within cased wells. It is entitled xe2x80x9cThrough-Casing Resistivity (TCR): Physics, Resolution, and 3-D Effectsxe2x80x9d having the authors of L. A. Tabarovsky, M. E. Cram, T. V. Tamarchenko, K. M. Strack and B. S. Zinger, of Atlas Wireline Services presented as Paper xe2x80x9cTTxe2x80x9d, Volume II, in the Transactions of the SPWLA Thirty-Fifth Annual Logging Symposium, Tulsa, Okla., Jun. 19-22, 1994 (hereinafter, Tabarovsky, et. al., 1994).
Other papers have been published relevant to measurements of formation resistivity from within cased wells including the following: (a) a paper entitled xe2x80x9cThe Electrical Field in a Borehole With a Casingxe2x80x9d by A. A. Kaufman, Geophysics, Vol. 55, No. 1, January 1990, p. 29-38; and (b) a paper entitled xe2x80x9cA Transmission-Line Model for Electrical Logging Through Casingxe2x80x9d, Geophysics, Vol. 58, No. 12, December, 1993, p. 1739-1747; (c) a technical report entitled xe2x80x9cFinal Report to ParaMagnetic Logging, Inc. for Numerical Analysis of D.C. Logging Through Metal Casingxe2x80x9d, having the authors of H. F. Morrison and C. J. Schenkel, Engineering Geoscience, College of Engineering, University of California, Berkeley, Calif., Nov. 22, 1991; and (d) a dissertation entitled xe2x80x9cThe Electrical Resistivity Method in Cased Boreholesxe2x80x9d, Dissertation for Doctor of Philosophy in Engineering: Materials Science and Mineral Engineering in the Graduate Division of the University of California at Berkeley, Berkeley, Calif., May 20, 1991.
Other recent articles appearing in various publications concerning the Through Casing Resistivity Tool(copyright) and/or the Vail Patents include the following: (a) an article entitled xe2x80x9cElectrical Logging: State-of-the-Artxe2x80x9d by Robert Maute of the Mobil Research and Development Corporation, in The Log Analyst, Vol. 33, No. 3, May-June 1992 page 212-213; and (b) in an article entitled xe2x80x9cThrough Casing Resistivity Tool Set for Permian Usexe2x80x9d in Improved Recovery Week, Volume 1, No. 32, Sep. 28, 1992.
The Vail Patents describe the various embodiments of the Through Casing Resistivity Tool(copyright) (xe2x80x9cTCRT(copyright)xe2x80x9d). Many of these Vail Patents describe embodiments of apparatus having three or more spaced apart voltage measurement electrodes which engage the interior of the casing, and which also have calibration means to calibrate for thickness variations of the casing and for errors in the placements of the voltage measurement electrodes. The TCRT(copyright) may be used for casing inspection procedures and to locate casing collars.
U.S. Pat. No. 4,796,186 which issued on Jan. 3, 1989 to Alexander A. Kaufman entitled xe2x80x9cConductivity Determination in a Formation Having a Cased Wellxe2x80x9d also describes an apparatus having three or more spaced apart voltage measurement electrodes which engage the interior of the casing and which also have calibration means to calibrate for thickness variations in the casing and for errors in the placements of the electrodes. This patent has been assigned to, and is owned by, ParaMagnetic Logging, Inc. of Woodinville, Wash. In general, different methods of operation and analysis are described in the Kaufman Patent compared to the Vail Patents cited above.
U.S. Pat. No. 4,837,518 which issued on Jun. 6, 1989 to Michael F. Gard, John E. E. Kingman, and James D. Klein, assigned to the Atlantic Richfield Company, entitled xe2x80x9cMethod and Apparatus for Measuring the Electrical Resistivity of Geologic Formations Through Metal Drill Pipe or Casingxe2x80x9d, predominantly describes two voltage measurement electrodes and several other current introducing electrodes disposed vertically within a cased well which electrically engage the wall of the casing, henceforth referenced as xe2x80x9cGard (518)xe2x80x9d. However, that patent does not describe an apparatus having three spaced apart voltage measurement electrodes and associated electronics which takes the voltage differential between two pairs of the three spaced apart voltage measurement electrodes to directly measure electronic properties adjacent to formations. Nor does Gard (518) describe an apparatus having at least three spaced apart voltage measurement electrodes wherein the voltage drops across adjacent pairs of the spaced apart voltage measurement electrodes are simultaneously measured to directly measure electronic properties adjacent to formations. Therefore, Gard (518) does not describe the methods and apparatus disclosed in the Vail Patents.
USSR Patent No. 56,026, which issued on Nov. 30, 1939 to L. M. Alpin, henceforth called xe2x80x9cAlpin (026)xe2x80x9d, which is entitled xe2x80x9cProcess of the Electrical Measurement of Well Casingsxe2x80x9d, describes an apparatus which has three spaced apart voltage measurement electrodes which positively engage the interior of the casing. However, the Alpin (026) does not have suitable calibration means to calibrate for thickness variations of the casing nor for errors related to the placements of the voltage measurement electrodes. Therefore, Alpin (026) does not describe the methods and apparatus disclosed in the Vail Patents.
French Patent No. 2,207,278 having a xe2x80x9cDate of Depositxe2x80x9d of Nov. 20, 1972 describes apparatus having four spaced apart voltage measurement electrodes which engage the interior of borehole casing respectively defined as electrodes M, N, K, and L. Various uphole and downhole current introducing electrodes are described. Apparatus and methods of operation are provided that determines the average resistance between electrodes M and L. French Patent No. 2,207,278 further explicitly assumes an exponential current flow along the casing. Voltage measurements across pair MN and KL are then used to infer certain geological parameters from the assumed exponential current flow along the casing. However, French Patent No. 2,207,278 does not teach measuring a first casing resistance between electrodes MN, does not teach measuring a second casing resistance between electrodes NK, and does not teach measuring a third casing resistance between electrodes KL. Various preferred embodiments described in the Vail Patents teach that it is of importance to measure said first, second, and third resistances to compensate current leakage measurements for casing thickness variations and for errors in placements of the voltage measurement electrodes along the casing to provide accurate measurements of current leakage into formation. Further, many embodiments of the Vail Patents do not require any assumption of the form of current flow along the casing to measure current leakage into formation. Therefore, for these reasons alone, French Patent No. 2,207,278 does not describe the methods and apparatus disclosed herein. There are many other differences between various embodiments of the Vail Patents and French Patent No. 2,207,278 which are described in great detail in the Statement of Prior Art for Ser. No. 07/754,965 dated Dec. 2, 1991 that issued as U.S. Pat. No. 5,223,794 on Jun. 29, 1993.
An abstract of an article entitled xe2x80x9cEffectiveness of Resistivity Logging of Cased Wells by A Six-Electrode Toolxe2x80x9d by N. V. Mamedov was referenced in TULSA ABSTRACTS as follows: xe2x80x9cIZV.VYSSH.UCHEB, ZAVEDENII, NEFT GAZ no. 7, pp. 11-15, Jul. 1987. (ISSN 0445-0108; 5 refs; in Russian)xe2x80x9d, hereinafter the xe2x80x9cMamedov (1987)xe2x80x9d. It is the applicant""s understanding from an English translation of that Mamedov (1987) that the article itself mathematically predicts the sensitivity of the type tool described in the above defined French Patent No. 2,207,278. Mamedov (1987) states that the tool described in French Patent No. 2,207,278 will only be show a xe2x80x9cweak dependencexe2x80x9d on the resistivity of rock adjacent to the cased well. By contrast, many embodiments of the Vail Patents, and the invention herein, provide measurements of leakage current and other parameters which are strongly dependent upon the resistivity of the rock adjacent to the cased well. Therefore, Mamedov (1987) does not describe the methods of measurement described herein.
U.S. Pat. No. 2,729,784, issued on Jan. 3, 1956 having the title of xe2x80x9cMethod and Apparatus for Electric Well Loggingxe2x80x9d, and U.S. Pat. No. 2,891,215 issued on Jun. 16, 1959 having the title of xe2x80x9cMethod and Apparatus for Electric Well Loggingxe2x80x9d, both of which issued in the name of Robert E. Fearon, henceforth called the xe2x80x9cFearon Patentsxe2x80x9d describe apparatus also having two pairs of voltage measurement electrodes which engage the interior of the casing. However, an attempt is made in the Fearon Patents to produce a xe2x80x9cvirtual electrodexe2x80x9d on the casing in an attempt to measure leakage current into formation which provides for methods and apparatus which are unrelated to the Kaufman and Vail Patents cited above. The Fearon Patents neither provide calibration means, nor do they provide methods similar to those described in either the Kaufman Patent or the Vail Patents, to calibrate for thickness variations and errors in the placements of the electrodes. Therefore, the Fearon Patents do not describe the methods and apparatus disclosed herein.
William Banning Vail III is the sole inventor of the apparatus and methods of operation of that apparatus described as the Through Casing Resistivity Tool(copyright) as set forth in the various Vail Patents defined above. William Banning Vail III has also conceived apparatus and methods of operation of the apparatus related to the Through Casing Resistivity Tool(copyright) that are relevant to casing inspection, to the location of collars, and for other inspection purposes set forth herein. Mr. Steven T. Momii has provided substantial inventive input concerning methods of operating the Through Casing Resistivity Tool(copyright) and related apparatus that are relevant to casing inspection, to the location of collars, and for other inspection purposes. The inventive input from Mr. Steven T. Momii has a bearing on at least one claim herein and he is therefore a co-inventor of the invention herein claimed. Therefore, the use of the Through Casing Resistivity Tool(copyright) or any portion thereof to measure casing inspection properties including collar location has been the joint work of both inventors as claimed herein. Consequently, a first portion of the disclosure shall concern specification concerning the Through Casing Resistivity Tool(copyright). A last portion of the disclosure shall concern the methods of operation of the Through Casing Resistivity Tool(copyright) and related apparatus for the purposes of casing inspection properties including collar location.
Accordingly, an object of the invention is to provide new apparatus and new methods of operation for the purposes of casing inspection.
It is yet another object of the invention to provide new apparatus and new methods of operation for the purposes of locating collars within cased wells.
It is another object of the invention to provide new apparatus and new methods of operation for the purposes of pipeline inspection.
It is yet another object of the invention to provide new apparatus and new methods of operation for the purposes of locating the joints where pipelines have been joined together.
It is yet another object of the invention to provide methods of operation of the Through Casing Resistivity Tool(copyright) for the purpose of casing inspection and for inspecting pipelines.
And it is finally another object of the invention to provide new methods of operation of the Through Casing Resistivity Tool(copyright) for the purpose of locating casing collars and for locating joints pipelines that are joined together.